This invention relates to an electric cell in which the positive electrode material is composed of an electro-conductive polymer composite of stainless steel integrated with an electroconductive polymer.
Attempts were made in the prior art to use electro-conductive polymers such as polyaniline, polypyrrole, polythiophen, polyacetylene, and poly-p-phenylene as electrode material for electric cells. Some are successful in producing commercially acceptable cells.
In constructing a cell using such a conductive polymer as the electrode material, a current collector is generally applied to the electrode. In order that the conductive polymer fully exert its function, the collector plays a great role. A careful choice must be made of the material, shape and contact of the collector.
As the collector for the conductive polymers, noble metals such as platinum and gold or carbonaceous materials are favorably used because of their stability and surface activity. However, noble metals such as platinum and gold are very expensive, leaving a cost problem. Carbonaceous materials are not regarded practical because they are less flexible and unreliable in strength.
On the contrary, the use of stainless steel as the collector is preferred because stainless steel is a commonly used material which is inexpensive and free of a strength problem. It is preferred to produce a conductive polymer such as polyaniline through electrolytic polymerization because the polymer is available in film form and an electrode used in electrolytic polymerization can be a collector as such. Stainless steel is generally used as the polymerization electrode in the form of a plate or foil. When a conductive polymer is deposited on a stainless steel substrate through electrolytic polymerization, the bond between the substrate and the deposit is insufficient. If a stainless steel substrate having a conductive polymer deposited thereon is used as the electrode without further processing, the polymer deposit tends to peel off or chip away from the substrate. It is thus difficult to obtain a flawless membrane material. Insufficent bond indicates that electrical contact is also insufficient. If such a conductive polymer composite is used to construct a cell in which the conductive polymer serves as an electrode active material and the stainless steel which has served as a polymerization electrode serves as a current collector, peeling or chipping of the conductive polymer or active material from the stainless steel or collector would often invite a loss of cell performance including a loss of collecting capacity and an increase of internal resistance of the collector.